SMTP is a protocol built upon TCP/IP, used for outgoing email transmissions, and email relaying. It uses ports 25 (clear) and 465 (SSL) by default.

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30
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6answers
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Lightweight outgoing SMTP server

What do you use as a lightweight SMTP for outgoing e-mails only? I am running an app that sends e-mails via SMTP when events occur once in a while, and I don't need a fully featured e-mail server. ...
35
votes
5answers
102k views

Can I set up system mail to use an external SMTP server?

Is it possible to set up system mail on a linux box to be sent via a different smtp server - maybe even with authentication? If so, how do I do this? If that's unclear, let give an example. If I'm at ...
10
votes
3answers
32k views

How to “close” open ports?

A few days ago I started to care a lot about my data security, I end up nmaping myself with: nmap 127.0.0.1 Surprise, surprise, I have lots of active services listen to localhost: $ nmap 127.0.0.1 ...
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votes
1answer
2k views

setting up a relay port for postfix smtp on CentOS 7

A CentOS 7 server has postfix, dovecot, and mailx installed. I am able to make an IMAP connection to the server from my remote Thunderbird client running on my local devbox. But I am not able to ...
3
votes
1answer
91 views

What is the correct helo for a smtp server that does not receive mail and does not have a FQDN?

What is the legal and correct helo for my SMTP server. Out going email only. Behind a NAT with no inbound ports open. SMTP server does not have a FQDN. Send mail for 2 different domains We are a ...
2
votes
1answer
562 views

assigning two ports to one service in firewalld

Is there a way to assign two ports to the same service in firewalld? For example, I would like for the SMTP service to listen on both port 25 and port 465. My first instinct is to change ...
2
votes
4answers
23k views

Helo command rejected: need fully-qualified hostname Error

My mail server is in some blacklist cause of spams. I reconfugured postfix. Aften then My customers get this error they can't send emails. 404 4.5.2 <PLLAMNAZIFE>: Helo command rejected: need ...
2
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2answers
1k views

How to send mail from a remote SMTP host?

I have Postfix suite installed locally on Ubuntu 10.10. I can send/receive mail to my local address, e.g. user@local.com. I'm given credentials to a remote mail server mailbox, e.g. ...
1
vote
0answers
155 views

How to disable SMTP auth plain for Citadel 8.20 on Slackware 14.0?

How do I turn off SMTP AUTH PLAIN for Citadel 8.20 on Slackware 14.0? If I set up postfix to handle SMTP would this allow me to not have SMTP auth plain enabled
0
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1answer
48 views

Is this the correct SPF DNS TXT syntax to allow the existing email servers (DNS MX records) and to authorize the new smtp server ip-address?

v=spf1 +mx ip4:65.1.2.3 -all Domain DNS TXT records to change: product1.com : sales@product1.com otherproduct.biz : sales@otherproduct.biz Information: Both domains have DNS MX records, and ...
0
votes
2answers
68 views

Can I send email in the background in Mutt while still being notified of errors?

Removing mutt's send delay I originally used mutt's built-in SMTP MTA. However, there is a considerable pause after hitting send. This can be disabled by using an external MTA with set ...
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votes
3answers
2k views

unable to view postfix email from centos 7 command line, why not?

I have postfix installed on a development box and I used the parameters from this other posting to configure postfix to work on localhost only. But the other posting does not explain how to send ...